The method returns the string that the notebook label should be filled with. This should be internationalised properly. This method is called once when the object is constructed, and again if the user triggers a relocale cascade to change their interface language.

This method is called on the object by the event handler for the "X" control on the notebook label, if it has one.

The method should generally initiate whatever is needed to close the tool via the highest level API. Note that while we aren't calling the equivalent menu handler directly, we are calling the high-level method on the main window that the menu itself calls.